Electron discharge device and circuit for high frequency oscillations



Feb. 28, 1939. N E UNDENBLAD 2,149,024

ELECTRON DISCHARGE DEVICE AND CIRCUIT FOR HIGH FREQUENCY OSCILLA'I'IONSOriginal Filed Nov. 28, 1934 2 Sheets-Sheet 1 f/ZAMf/VT 15455 FORM 77/460 (7/?(0/7' 70 MAM/m" sup/u y MLS E. LINDENBLAD Feb. 28, lg N E.LINDENBLAD 2,149fi24 ELECTRON DISCHARGE DEVICE AND CIRCUIT FOR HIGHFREQUENCY OSCILLATIONS Original Filed Nov. 28, 1934 2 Sheets-Sheet 2mywiz/c 3 INVENTOR ATTORNEY Patented Feb. 28, 1939 UNITED STATESELECTRON DISCHARGE DEVICE AND CIR- CUIT FOR HIGH FREQUENCY OSCILLA-TIONS Nils E. Lindenblad, Port Jefferson, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application November28, 1934, Serial No. 755,153 Renewed September 1, 1938 26 Claims.

The present invention relates to high frequency oscillation circuits,and particularly to a novel method of and apparatus for producing ultrahigh. frequency oscillations.

One of the objects of the present invention is to provide an ultra highfrequency oscillator which depends for its operation upon the time oftravel of electrons between the elements of the tube.

In accordance with the principles of the present invention, there isprovided an oscillation generation circuit comprising a tube having twofilaments and a ring-like or cylindrical anode between them. A strongmagnetic field functions to influence the electrons emanating from onefilament to travel to the vicinity of the other filament; consequentlythe electrons pass through the field of the anode. The ring-like anodeand magnetic field thus act as electron' 1enses, making each filamentlie in the focus of emission from the other. In this way, the time takenfor the electrons to travel from one filament to the other issubstantially independent of the path taken by the electrons. It hasbeen found that under these conditions, the tube is in unstableequilibrium and capable of producing push-pull oscillations between thefilaments, at any frequency to which the filaments are tuned, up to thepoint where the time of travel of the electrons becomes appreciablecompared with the time of one cycle of oscillation.

A better understanding of the invention may be had by referring to thefollowing detail description which is accompanied by drawings, wherein:

Fig. 1 illustrates schematically an oscillator circuit embodying theprinciples of the present invention;

Fig; 2 illustrates another embodiment with several refinements over thatof Fig. 1;

Figs. 2a and 2b illustrate cross sectional views of details forobtaining more concentrated beam focusing of the electrons;

Fig. 3 illustrates diagrammatically how the system may be cascaded;

Fig. 4 schematically illustrates one way in which the oscillator may beused for reception of radio waves; and

Fig. 5 illustrates a modification wherein the electron discharge deviceof the invention is provided with grids.

Referring to Fig. 1, there are shown two sources of electrons, namelyfilaments F1 and F2, one on.

each side of an anode G in the form of a shield with a hole in thecenter thereof, the filaments being axially aligned with the axis of thehole shields S1, S2 in back of the filaments.

in the anode. The elements of the tube are subjected to a linearmagnetic field between poles N1, N2, which field is co-axial with theelectrode system F1, G, F2. For directing the emission of the electronsmore or less in a cone toward the hole in; the anode G, there areprovided suitable A source of energy P supplies a high positivepotential to the anode G with respect to the filaments.

The motion of the electrons emanating from the filaments F1, F: Will,with the exception of those that'move axially, have a projected orcomponentmotion at right angles to the axis of the system, and also atright angles to the magnetic field. This projected motion, which in itsorigin was intended to be linear, is transformed into a circular motionby the magnetic field. The total motion of an electron will thereforedescribe a curve or helix.

As the group motion of the emitted electrons is represented by a coneexpanding toward the I shield G, the helix will also be expanding. Theelectrons, however, are kept from striking the anode and are directedthrough the hole thereof by the magnetic field which tightens up thehelical path of the electrons. Due to the minuteness of the size of anelectron and their tremendous number, there is no effect on theoperation of the system by collisions between electrons emanating fromthe opposite filaments. An analogous situation takes place in Barkhausenand magnetron circuits wherein electrons function under similarconditions.

While the electrons are travelling towards the anode G, they aresubjected to an accelerating force from the electromotive force on theanode. After passing through the hole in the anode and towards the otherfilament, the accelerating force changes to a retarding force as theelectrons now travel away from the anode. Their motion is consequentlyslowed down and the magnetic field therefore exerts a greater andgreater influence on the curvature of their path; the helical spiral istightened up and the electrons which were diverging from one another onthe launching side of the anode are now converging toward the oppositefilament. This phenomenon of changing a. diverging beam into aconverging beam is known as electron focusing.

Oscillations are produced in the following manner. The electronsarriving at the filament opposite the one from which they originate,have, upon their arrival, lost all their velocity due to a retardingforce'to which they have been subjected since their passage through thehole in the anode G They will, therefore, much in the same fashion as inthe case of a returning electron in a Barkhausen or in a magnetron tube,form a cloud around the filament with a subsequent effect of cutting offemission from this filament. The cloud represents a negative chargewhich greatly or entirelyneutralizes the gradient around the filament asproduced by the positive electromotive force on the anode shield G. Inother words, the electrons arriving at a filament opposite the one fromwhich they have emanated, will cause the emission of the nearestfilament to be interrupted or decreased because of the accumulated spacecharge. This space charge will disperse and the action will be repeatedin the opposite direction. Thus, the time of travel or velocity of theelectrons, plus the time required for the space charge to disperse, willdetermine the frequency of oscillation. The push-pull functioning of thesystem may perhaps be explained by making an analogy to the difiicultyof trying to balance an egg on end. If there is the least unbalance, thedisturbance will increase or regenerate because the system isintrinsically unstable. In the present invention push-pull tuning ismade correct and to coincide with the direct current voltage and themagnetic field adjustment which determines the transit time of theelectrons, and thus the push-pull tuning is synchronized with theelectron transit time.

Returning to the consideration of the convergence effect, it will benoted that this is spherical or, as has been previously expressed,conical. The convergence effect, of course, is not that of a fullsphere, although it is possible to makethe angle of the cone largeenough to exceed the two dimensional convergence of a cylinder. A threedimensional convergence effect will, of course, cause better emissioncut off than a two dimensional effect.

It is preferred that the two filaments be connected together to form atuned circuit in order to transmit to external circuits the oscillatingpower generated within the system. The electrons, however, in theiroscillatory motion, may find suflicient radiation resistance so as toradiate directly, in which case one may simply mount the tube directlyin the focus of a mirror M which has its axis parallel with the axis ofthe tube in order to obtain radiation.

Fig, 2 shows an arrangement which has been used with good results. Thelocation and approximate dimensions of the elements of the tube, whichwere enclosed in a UX852 envelope, are shown. In this figure thefilament leads, which are energized from sources of energy I and 2, andthe lead from the anode ring G are enclosed in tubular shields 3, l, and5 respectively. A sliding tuning element 6 is shown shunted across thefilament shields 3 and 4 for aiding in filament tuning. The anode shield5 is shown grounded for radio frequency currents through a condenser 1.With the arran ement indicated in this figure. it was noticed uponvarying the voltage applied to the anode, that the frequency ofoscillation is determined for lower anode voltages to a greater extentby the length of the tuning circuit, while at the higher voltages theanode voltage and magnetic field seem to be the factors determining thefrequency. This is evidenced by sharper tuning effects at high anodevoltages and magnetic fields, by varying the latter factors than byvarying the tuning circuit.

From the tests made, indications are that the filaments oscillate 180degrees out of phase with respect to each other while the anode is atzero radio frequency potential.

As indicated in Figs. 2a and 2b, and in accordance with the principlesof the present invention, the phenomenon of changing a diverging beaminto a converging one may be accomplished simply by electrostatic meansalone. In the present case the space circuit over which the electronstravel is made to behave in similar manner in two directions of the axis(back and forth). These figures only indicate diagrammatically and byway of illustrating the principles involved, simple arrangements of anall electric, two-way focusing scheme. The systems shown in thesefigures are considered to be more efficient than that of Fig. 1 becauseof their high convergence effect.

Inasmuch as the system of Fig. 1 can be looked upon as either a doubleacting split plate magnetron or as a double acting Barkhausenarrangement, it can be equipped with symmetrical tuning circuits, whichin itself is a great advantage. Higher frequencies may be obtainablewith the tube of the system operating in a manner similar to aBarkhausen-Kurz or a Gill-Morell oscillator.

Fig. 3 indicateshow the system of the invention may be cascaded. Insteadof allowing the electrons to return to their original filament afterhaving arrived at the second filament, it is proposed to have theelectrons continue their journey towards another positive shield,whereupon they are finally permitted to return after having passedthrough their second positive shield. The arrows show the direction ofthe magnetic field. The electrons here cascade from one section of thedevice into the next section, the purpose being to' get synchronizationbetween the two sections so that their outputs may easily integrate.After having left the filament at one end of the device, the electronsare focused together as toward the second filament as in the simple casealready described in connection with Fig. 1. There is, however. nofilament at the second converging point. This filament is replaced by ashield O with a small hole through which the electrons may pass. shieldthe electrons emerging through the hole act as a source of emission.This emission then spreads toward a second anode and is thereafterfocused toward another hole. Where the series of cascades terminate theelectrons are finally focused toward a second filament where they mayturn around and go through the whole cascade in the o posite direction.

Fig. 4 illustrates diagrammatically, the application of the oscillatorto a radio receiving circuit. In this fi ure the two filaments aresupplied in parallel from a common filament supply source, and theenergizing leads 8 for the filaments are enclosed within a metal tube 9.For receiving the radio waves there is provided an antenna I which iscoupled to the filament tuning circuit by means of connections H, Hwhich extend from stra s i3 and I4 surrounding the tube 9 to taps l andIS on antenna l0, these taps being so spaced as to match the impedanceof the antenna. The two terminals of the interelectrode space. which arethe filaments F1 and F2. receive voltage excitation from the incomingsignal which signal is detected in the anode circuit.

It is to bev understood that the invention may be employed in bothtransmitting and receiving circuits and is not limited to the precisestructure shown in the drawings, since various modi- On the other sideof thismodulation circuit.

fications may be made without departing from the spirit and scopethereof. For example, if desired, the electron discharge device of theinvention may be used as an amplifier, and if used as an oscillator in atransmitter may be anode modulated in Heising fashion. Also an auxiliarygrid may be placed in the vicinity of each cathode for improving theaction of the device, each grid being maintained preferably at anegative potential with respect to its associated cathode.

Such an arrangement is disclosed in Fig. 5,

wherein the grid may be connected to a suitable The centers of the gridsmay, if desired, coincide with the axis of the tube.

In devices in general based upon pendulum action of electrons (like theBarkhausen, magnetron, etc.) the electrons are originally accelerated bythe anode. If the other electrodes carry insuflicient potential toattract the electrons to such a degree that they (the other electrodes)become bombarded, the electrons will describe a to and fro motion. Sinceelectrons are electric charges, they cause opposite charges to bedistributed over the electrodes. As the electrons move, the charges ontheelectrodes vary. The change in charge on the electrodes then causeselectric currents to flow in the external circuit connected to the eectrodes. This is the way in which the electron motions induce currentsin the external circuit. If the external circuit is resistively loaded,not only by its own circuit loss, but, by useful load, the currentproduced in the external circuit produces an ohmic voltage drop which issuch that it varies the electrode potential in opposition to theelectron motion. This is simply Lentz law applied to thermionic devices.It can therefore be seen that the electrons are retarded as they performwork in the external circuit; their motion is attenuated. We have so farconsidered only the motion of one electron. If the electrons move aboutat random, it is easily understood that the motion of one cancels theeffect of the motion of another and no Work is performed in the externalcircuit. Their motion is then not attenuated. It is, therefore,necessary that the electrons be organized into groups. This is done invarious ways. In the conventional triode feedback circuit the throttlingeffect of the grid produces this organization. In this case electronsonly flow intermittently, i. e., there are no disorganized electrons atany time. In electron pendulum devices such as Barkhausen, the magnetronand the device of the present invention, electrons are always present inthe interelectrode space. The efliciency of these devices depends uponthe de ree to which these eectrons may be organized. Thus for certainelectric and magnetic fields the electrons will oscillate but at randomand their oscillation gives no external evidence. Organization isobtained when the electrons begin to fall into groups. This groupformation is, for instance, produced by space charges around the pointwhere the electrons turn around. When the anode voltage is applied,electrons are accelerated toward it. Some reach the anode on their firsttrip and the high ln'netic energy they possess at the time of collisionis a great loss. Some miss the anode and pass on. They are then retardedand will eventually come to a standstill and turn around. Whenevertraffic on a highway slows down, congestion occurs; so with theelectrons. Electron congestions are equivalent to space charges andspace charges produce electric fields. Now, the electrons which arrivefirst at the turning point are kept there a little longer by the laterarriving or oncoming electrons and the later ones are made to turnaround a little sooner due to the negative charge from the earlierarriving electrons. This action thus promotes group formation ororganization. The electrons can now perform work in the external circuitand become attenuated in their to and fro motion. The electrodepotential from a signal of course also has such organizing eifects. Thusif the device is adjusted so that the electrons oscillate at the rightfrequency but at random by having such a magnetic field that theelectrons largely miss the anode, the incoming signal will produceorganization and the electrons will receive attenuated motion since (asa group) they now act on the external circuit. When the electrons areattenuated, the field conditions are no longer-correct to keep theelectrons from landing on the anode. This then indicates both why thedevice works as a detector and as an amplifier; as an amplifier becausemost of the energy of the electron motion is already given by theelectric field. The signal to be amplified only needs to supply theorganizing eiTect.

What is claimed is:

l. The method of producing high frequency oscillations which comprisesprojecting a stream of electrons in one direction in conical fashion,causing said stream of electrons to first diverge and then converge,projecting another stream of electrons in an opposite direction in asimilar manner, and reversing the directions of travel of said streams.

2. The method of producing high frequency oscillations which comprisesprojecting from a pair of reference points two streams of electrons inopposite directions, applying a magnetic field axially to the maindirection of travel of said streams of electrons, and causing eachstream to converge at the point of origination of the other stream.

3. A high frequency oscillator comprising a' pair of relativelyconcentrated electron emitting elements and an anode with a centralaperture located between said elements, all within a single envelope,said elements being axially aligned with the axis of said aperture, asource of energy for applying a positive potential to said anode withrespect to said electron emitting elements, and means for focusing theelectrons around the electron emitting element toward which they aretravelling after having passed through the aperture of said anode.

4. A high frequency electron discharge device comprising a pair ofelectron emitting elements and an anode with a central aperture locatedbetween said elements, all within a single envelope, said elements beingaxially aligned with the axis a positive potential to said anode withrespect to said electron emitting elements, and a magnetic field axiallydisposed with respect to the electron emitting elements and the apertureof said anode for influencing the electrons to travel in a helical pathand for focusing the electrons around the element towards which they aretravelling after having passed through the aperture of said anode,whereby substantial electron emission cutoff is momentarily effected.

5. A high frequency oscillator comprising a pair of relatively highlyconcentrated electron emitting elements, a shield for each of saidelements arranged to aid in directing the electrons toward the otherelectron emitting element, an anode with a central aperture locatedbetween with a central aperture located between said ele-- ments, allwithin a single envelope, said elements being axially aligned with theaxis of said aperture, a source of energy for applying a positivepotential to said anode with respect to said electron emitting elements,and means for focusing the electrons around the element toward whichthey are travelling after having passed through the aperture of saidanode, said means comprising ring-like shields on both sides of saidanode and being provided with apertures to enable the electrons to passthrough them, and a source of energy for, applying negative potentialsto said shields with respect to said electron emitting elements; a I

7. A high frequency oscillator comprising a pair of electron emittingelements and an anode with a central aperture located between saidelements, all within a single envelope, said elements being axiallyaligned with the axis of said aperture, a sourcecofenergy for applying apositive potential to said anode with respect to said electron emittingelements, and means for focusing the electrons around the element to-'ward which they are travelling after having passed through the apertureof said anode, a

pair of leadsforeach of said electron emitting elements extendingexternally from said envelope' to a source of heating current, and atuning element coupled to said leads for tuning same.

8. A high frequency oscillator comprising a for focusing the electronsaround the element toward which they are travelling after having passedthrough the aperture of said anode, a pair of leads for each of saidelectron emitting elements extending externally from said envelope to asource of heating current, a lead extending from said anode to saidfirst source of energy, a tubular shield surrounding each of said pairsof leads and a tubular shield surrounding said anode lead, and anadjustable strap connected across the tubular shields for said two pairsof leads for tuning said oscillator.

9. A high frequency oscillator comprising a pair of electron emittingelements and an anode with a central aperture located between saidelements, all within a single envelope, said elements being axiallyaligned with the axis of said aperture, a source of energy for applyinga positive potential to said anode with respect to said electronemitting elements, and means for focusing the electrons around theelement toward which they are travelling after having passed through theaperture of said anode, a pair of leads for each of said electronemitting elements extending externally from said envelope to a source ofheating current,a lead extending from said anode to said first source ofenergy, a tubular shield surrounding each of said pairs of leads and atubular shield surrounding said anode lead, and an adjustable strapconnected across" the tubular shields for said two pairs of leads fortuning said oscillator, and a condenser, one

plate of which is connected to ground and the other of which isconnected to said tubular shield surrounding said anode lead.

10. A high frequency oscillator comprising a pair of electron emittingelements, a shield for each of said elements arranged to aid indirecting the electrons toward the opposite element, an anode with acentral aperture located between saidelements, all within a singleenvelope, a source of energy for applying a positive potential to saidanode with respect to said electron emitting elements, and ameans forapplying a magnetic field which is axially disposed with respect tothe-electron emitting elements and the aperture ofsaid anode forinfluencing the electrons to travel in a helical path and for focusingthe electrons around the electron emitting element towards which theyare travellingafter having passed through the aperture of said anode, apair of leads for each of said electron emitting elements extendingexternally from said envelope to a source of heating current, a leadextending from said anode to said first source of energy, a tubularshield surrounding each of said pairs of, leads and a tubular shieldsurrounding said anode lead, and an adjustable strap connected of leadsfor tuning said oscillatonand a condenser, one plate of which isconnected to ground a and the other of which is connected to saidtubudischarge device comprising a pair of electron emitting elements andan anode with a central aperture located between said elements, allwithin a single envelope, said elementsb'eing axially aligned with theaxis of said aperture, a source of energy for applying a positivepotential to said anode with respect to said electron emitting elements,means including leads for heating said electron emitting elements, areceiving antenna, connections coupling said leads to said antenna, anda utilization circuit including apparatus for detecting the signallocated between said anode and said source of energy.

12. In combination, an electron discharge device having within a singleenvelope a hollow cylindrical anode, and a pair of electron emittingelements oppositely disposed with respect to said anode, the latterbeing so arranged that there is an unobstructed passage from oneelectron emitting element to the other, an external source of energy forapplying a positive potential to said anode with respect to saidelectron emitting elements, a tuned circuit coupled between said pair ofelectron emitting elements and conductively connected thereto, oneterminal of said source being connected to said anode and the otherterminal of said source being connected substantially to the center ofsaid tuned circuit, and a focusing coil for causing the electronsemanating from one of said elements to focus around the other electronemitting element.

13. The method of producing high frequency oscillations which comprisesprojecting a stream of electrons in one direction, causing said streamto first diverge and then converge, and reversing the direction oftravel of said stream in the same order.

across the tubular shields for said 'two pairs stream ,of electrons tofirst diverge, and then converge, then diverge, and then converge, andprojecting another stream of electrons in an opposite direction in asimilar manner.

15. In combination, a high frequency electron discharge deviceoscillator having a pair of heated electron emitting elements, and ananode with a central aperture located between said ele:

ments, all within a single envelope, a source ofenergy for applying apotential to said anode which is positive with respect to the electronemitting elements, a tuned circuit comprising an inductance andcapacitance located between and conductively coupled to said electronemitting elements, and magnetic means adjacent said envelope forapplying a magnetic field to the path of travel of said electrons forinfluencing the motion of said electrons.

16. In combination, a high frequency electron discharge device having apair of heated electron emitting elements, and an anode with a centralaperture located between said elements, all within a single envelope, asource of energy for applying a potential to said anode which ispositive with respect to the electron emitting elements, a tuned circuitcomprising an inductance located between said electron emittingelements, and a coil adjacent said envelope for applying a magneticfield to the path of travel of said electrons for influencing the motionof said electrons, a source of oscillations coupled to said. tunedcircuit, and a. utilization circuit coupled to said anode.

1'7. A high frequency oscillator comprising a pair of electron emittingelements and an anode with a relatively wide central aperture locatedbetween said elements, all within a single envelope, said electronemitting elements having an appreciably smaller emitting area than thearea of said central aperture of said anode, said elements being axiallyaligned with the ams of said aperture, a source of energy for applying apositive potential to said anode with respect to said electron emittingelements, and means for focusing the electrons around the electronemitting element toward which they are travelling after having passedthrough the aperture of said anode.

18. A high frequency oscillator comprising a ing the electrons towardthe element on the opposite side of said anode, and means for focusingthe electrons around the electron emitting element toward which they aretraveling after having passed through the aperture of said anode,whereby substantial electron emission cutoff is momentarily effected.

19. A high frequency oscillator comprising a pair of electron emittingelements and an anode with a relatively wide central aperture locatedbetween said elements, all within a single envelope, said electronemitting elements having an appreciably smaller emitting area than thearea of said central aperture of said anode, said elements being axiallyaligned with the axis of said aperture, a source of energy for applyinga positive potential to said anode with respect to said electronemitting elements, and means for focusing the electrons around theelectron emitting element toward which they are travelling after havingpassed through the aperture of said anode, and a curved shield behindeach electron emitting element for aiding in directing the electronstowards the other electron emitting ele- .ment.

20. A high frequency oscillator comprising a pair of electron emittingelements and an anode with a central aperture located between saidelements, all within a single envelope, said elements being axiallyaligned with the axis of said aperture, a source of energy for applyinga positive potential to said anode with respect to said electronemitting elements, a grid having a central aperture located between eachelectron emitting element and said anode, and means for maintaining eachof said grids at a negative potential relative to its associatedelectron emitting element.

21. An oscillation generationsystem co'mprising within a single envelopea pair of heated sources of electrons, an element permitting the passageof electrons located between said sources, a resonant circuit connectingsaid sources together, means for maintaining said element at a positivepotential relative to said sources, said resonant circuit being tuned tohave its natural frequency correspond substantially to the frequency ofelectron oscillation between said sources.

22. In combination in a receiver, a high frequency electron dischargedevice having a pair of heated electron emitting elements, and an anodewith a central aperture located between said elements, all within asingle envelope, a source of energy for applying a potential to saidanode which is positive with respect to the electron emitting elements,a tuned circuit located between said electron emitting elements, andmagnetic means adjacent said envelope for applying a magnetic field tothe path of travel of said electrons for influencing the motion of saidelectrons.

23. In combination, a high frequency electron discharge deviceoscillator having a pair of electron emitting elements, and an anodewith a central aperture located between said elements, all within asingle envelope, a source of energy for applying a potential to saidanode which is positive with respect to the electron emitting elements,a tuned circuit comprising an inductance and capacitance located betweenand conductively coupled to said electron emitting elements, andmagnetic means adjacent said envelope for applying a magnetic field tothe path of travel of said electrons for influencing the motion of saidelectrons.

24. In combination, a high frequency electron discharge device having apair of electron emitting elements, and an anode with a central aperturelocated between said elements, all within a single envelope, a source ofenergy for applying a potential to said anode which is positive withrespect to the electron emitting elements, a tuned circuit comprising aninductance located between said electron emitting elements, and a coiladjacent said envelope for applying a magnetic field to the path oftravel of said electrons for influencing the motion of said electrons, asource of oscillations coupled to said tuned circuit, and a utilizationcircuit coupled to said anode.

25. An oscillation generation system compris= ing within a single,envelope a pair of sources of electrons, an element permitting thepassage of electrons located between said sources, a resonant circuitconnecting said sources together, means for maintaining said element ata positive potential relative to said sources, said resonant circuitbeing tuned to have its natural frequency correspond substantially tothe frequency of electron oscillation between said sources.

26. In combination in a receiver, a high frequency electron dischargedevice having a pair of electron emitting elements, and an anode with acentral aperture located between said elements},

all within a single envelope, a source of energy for applying apotential to said anode which is positive with respect to the electronemitting elements, a tuned circuit located between said electronemitting elements, and magnetic means adjacent said envelope forapplying a magnetic field to the path of travel of said electrons forinfluencing the motion of said electrons.

NILS E. IANDENBLAD.

